1. Field of the Invention
The present invention relates to a motor generator, and more particularly, to a motor generator that can be applied to an electric vehicle such as a pure electric vehicle (PEV), a hybrid electric vehicle (HEV) and a fuel cell electric vehicle (FCEV), a high power aerogenerator, and a generator for an internal combustion engine.
2. Description of the Related Art
A hybrid electric vehicle provided with a drive system including an internal combustion engine and an electric motor has two types of batteries, that is, a high voltage battery for driving the electric motor and a low voltage battery for driving an accessory of the vehicle such as a lamp unit and audio equipment. The high voltage battery is configured to be charged by a motor generator mounted in the vehicle.
FIG. 28 represents the configuration of a conventional hybrid electric vehicle. The hybrid electric vehicle is configured to transmit power output from an internal combustion engine 101 and/or an electric motor 102 to wheels via a drive train 103. The electric motor 102 is driven and controlled with power from a high voltage battery 104 via a power converter 105. An alternator 106 generates electric power in conjunction with the operation of the internal combustion engine 101 so as to charge the low voltage battery 107. Upon charging of the high voltage battery 104, the electric motor 102 is activated to serve as the generator and charges the high voltage battery 104 via the power converter 105.
There is also a known hybrid electric vehicle having the low voltage battery 107, which is charged by the high voltage battery 104 via a DC-DC converter instead of using the alternator 106.
Various kinds of motor generators of field winding type have been proposed. For example, Japanese Patent Laid-Open Publication No. 6-105512 discloses the motor generator having two windings, one connected to the high voltage battery, and the other connected to the low voltage battery.
The drive system for the known electric vehicle requires motor generators for the high-voltage system for the drive system and for the low voltage system for accessories, respectively, or requires a single motor generator and the DC-DC converter. This may cause increase not only in space to accommodate those units but also in cost.
In the case where the motor generator of the field winding type having two windings is employed, and one of those windings is wound for driving the vehicle, the size of the motor generator becomes so large that it cannot be mounted on the vehicle. Additionally, it is difficult to control the aforementioned windings simultaneously because of the field winding type.